RESUMEN

In the process of using the Distributed Radar Network Localization System (DRNLS) further to improve the survivability of a carrier platform, the random characteristics of the system's Aperture Resource Allocation (ARA) and Radar Cross Section (RCS) are often not fully considered. However, the random characteristics of the system's ARA and RCS will affect the power resource allocation of the DRNLS to a certain extent, and the allocation result is an essential factor determining the performance of the DRNLS's Low Probability of Intercept (LPI). Therefore, a DRNLS still has some limitations in practical application. In order to solve this problem, a joint allocation scheme of aperture and power for the DRNLS based on LPI optimization (JA scheme) is proposed. In the JA scheme, the fuzzy random Chance Constrained Programmin model for radar antenna aperture resource management (RAARM-FRCCP model) can minimize the number of elements under the given pattern parameters. The random Chance Constrained Programmin model for minimizing Schleher Intercept Factor (MSIF-RCCP model) built on this basis can be used to achieve DRNLS optimal control of LPI performance on the premise of ensuring system tracking performance requirements. The results show that when RCS has some randomness, its corresponding uniform power distribution result is not necessarily the optimal scheme. Under the condition of meeting the same tracking performance, the required number of elements and power will be reduced to a certain extent compared with the number of elements in the whole array and the power corresponding to the uniform distribution. The lower the confidence level is, the more times the threshold is allowed to pass, and the lower the power is, so that the DRNLS can have better LPI performance.

RESUMEN

With the widespread application of unmanned aerial vehicle (UAV) formation technology, it is very important to maintain good communication quality with the limited power and spectrum resources that are available. To maximize the transmission rate and increase the successful data transfer probability simultaneously, the convolutional block attention module (CBAM) and value decomposition network (VDN) algorithm were introduced on the basis of a deep Q-network (DQN) for a UAV formation communication system. To make full use of the frequency, this manuscript considers both the UAV-to-base station (U2B) and the UAV-to-UAV (U2U) links, and the U2B links can be reused by the U2U communication links. In the DQN, the U2U links, which are treated as agents, can interact with the system and they intelligently learn how to choose the best power and spectrum. The CBAM affects the training results along both the channel and spatial aspects. Moreover, the VDN algorithm was introduced to solve the problem of partial observation in one UAV using distributed execution by decomposing the team q-function into agent-wise q-functions through the VDN. The experimental results showed that the improvement in data transfer rate and the successful data transfer probability was obvious.

RESUMEN

Activated carbon (AC) is widely used in pollutant removal, due to its adsorption capacity, conductivity and catalytic performance. However, few studies focus on the redox activity of AC and its role in pollutant transformation. In this study, we found that AC could efficiently mediate the oxidation of As(III) and the process of As(III) oxidation was pH and oxygen concentration dependent. In general, the presence of O2 promoted As(III) oxidation at pH 3.0-9.5. Acidic and alkaline conditions favored As(III) oxidation regardless of whether there was oxygen, but the mechanisms involved were quite different when there was oxygen. At pH 3.0, reactive species (H2O2 and ·OH) were generated and accounted for As(III) oxidation; at pH 9.5, As(III) was directly oxidized by O2 (electron transfer from As(III) to O2 mediated by carbon matrix) under aerobic conditions. Pre-oxidation and cyclic experiments results indicated the ability of AC to oxidize As(III) at pH 9.5 was sustainable and recyclable. This study provided a new insight in pollutant oxidation by AC in the environment.

Asunto(s)

Arsénico , Carbón Orgánico , Adsorción , Catálisis , Peróxido de Hidrógeno , Oxidación-Reducción

RESUMEN

Space-time adaptive processing (STAP) techniques have been motivated as a key enabling technology for advanced airborne radar applications. In this paper, a slow-time code design is considered for the STAP technique in airborne radar, and the principle for improving signal-to-clutter and noise ratio (SCNR) based on slow-time coding is given. We present two algorithms for the optimization of transmitted codes under the energy constraint on a predefined area of spatial-frequency and Doppler-frequency plane. The proposed algorithms are constructed based on convex optimization (CVX) and alternating direction (AD), respectively. Several criteria regarding parameter selection are also given for the optimization process. Numerical examples show the feasibility and effectiveness of the proposed methods.

RESUMEN

Previous studies have demonstrated that pyrogenic carbon can mediate the reductive degradation of pollutants in solutions containing reducing reagents under anaerobic conditions. However, few studies have investigated oxidative species formation and pollutants transformation directly mediated by pyrogenic carbon under aerobic conditions. In this study, we found that activated carbon (AC) can not only mediate reductive hexachloroethane degradation in the absence of O2 but also mediate the oxidation of As(III) and sulfanilamide in L-Cysteine (Cys, a naturally abundant thiol compound) solution under aerobic conditions. Electron paramagnetic resonance and quenching studies indicated that O2•-, H2O2 and •OH was formed in Cys/AC system under aerobic conditions. High O2 content favored the formation of •OH, indicating that O2 participated in •OH production. In addition, an increase in AC concentration and specific surface area led to increased formation of •OH, and other pyrogenic carbon materials such as biochar and graphite were also found capable of mediating the formation of •OH. This study demonstrates that pyrogenic carbon could mediate •OH formation in solutions containing reductive reagents under aerobic conditions, which provides a new perspective for studying the behavior of pyrogenic carbon in the environment and its role in biogeochemical processes.

RESUMEN

: To solve the problem of dwell time management for multiple target tracking in Low Probability of Intercept (LPI) radar network, a Nash bargaining solution (NBS) dwell time allocation algorithm based on cooperative game theory is proposed. This algorithm can achieve the desired low interception performance by optimizing the allocation of the dwell time of each radar under the constraints of the given target detection performance, minimizing the total dwell time of radar network. By introducing two variables, dwell time and target allocation indicators, we decompose the dwell time and target allocation into two subproblems. Firstly, combining the Lagrange relaxation algorithm with the Newton iteration method, we derive the iterative formula for the dwell time of each radar. The dwell time allocation of the radars corresponding to each target is obtained. Secondly, we use the fixed Hungarian algorithm to determine the target allocation scheme based on the dwell time allocation results. Simulation results show that the proposed algorithm can effectively reduce the total dwell time of the radar network, and hence, improve the LPI performance.

RESUMEN

The Surface enhanced fluorescence (SEF) and Surface Enhanced Raman Scattering (SERS) of Au nanoparticle films deposited on Si and SiO2 substrates are presented. From the experimental results, it is concluded that the fluorescence peak intensity changes in a similar way with the Raman intensity for the various substrates. Both the fluorescence and the Raman intensity were much stronger on SiO2 substrate than on the Si substrate. That is due to the Crystal Violet (CV) adsorbed on the substrate having different refractive index effect the electrical field near the nanoparticles. The nanoparticle size effect on the Raman and fluorescence was also studied.